The present invention is an advance in the art of delivery systems for the gradual release of active agents. This invention enables an active agent to be gradually released through the direct interaction of the agent and a solvent either within channels in the structure enclosing the active agent or through exposure of the active agent to the solvent when the structure enclosing the active agent is deformed.
Prior to the present invention, the gradual release of active agents, such as drugs, could be accomplished by the diffusion of the active agent through an encapsulating material. A discussion of such encapsulated structures is found in R. Dunn and D. Lewis, Fibrous Polymers for the Delivery of Contraceptive Steroids to the Female Reproductive Tract, Controlled Release of Pesticides and Pharmaceuticals 125-46 (D. Lewis ed. 1981), which describes fiber-like structures. Alternatively, an encapsulating shell around the active agent could be ruptured causing exposure of the active agent to various solvents.